Apparatus for starting and operating electric discharge lamp



Feb. 11, 1958 M. G. CLARKE ET AL APPARATUS FOR STARTING AND OPERATING ELECTRIC DISCHARGE LAMP Filed Oct. 2, 1952 Inventors: Maurice G.C|ar-ke,

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Herbert. LiFrivett,

Their- Attcr ney 2,823,337 'Patented Feb. 11, 1958 APPARATUS FOR STARTINGAND OPERATING i ELECTRIG DISCHARGE LAMP Maurice' iGffClarke andHerbert L."Privett, 'Rugby,Eng-

' land, assignors, by mesne assignments, to Generai Elec- 'tric Company, a co'rporation'of New. York Application OctoberZ, 1952,-'Scrial No. 312,786

4 Claims. ,(Cl; 315-98) This invention relates to apparatus for starting and operating electric discharge lamps of the type having a low pressure-gas or vapor filling,- particularly mercury vapor with" a rare gas, and filamentary electron emissive electrodes spacedwithin awitreousenvelope having its -inner-wa]l' coated with luminescent material. Such lamps -are commonly known as low pressure fluorescent discharge lamps.

In a known apparatus for operating a lamp. ofsthis type,- the discharge between theelectrodes has beenini- .tiated by heating the electrodes to. their electrons emitting temperature and then causing the discharge to strike by a high voltage surge, a thermostatically operated starter switch being employed to delay the surge until the said electrodes have reached their electron emitting stage. More recently starting and operating apparatus has been employed to initiate the discharge instantly without the delay caused by the thermal starting switch. One common method of achieving this result has been to use apparatus comprising an electrode heating transformer having secondary windings for supplying the heating current to the electrodes, the primary winding being connected to the supply mains in series with the stabilizing choke, and for this purpose a grounded starting strip or stripe has been attached to the lamp. This starting strip usually consists of a thin coating of conductive substance along the length of the lamp, the effect of which is to counteract the electrostatic efiect of the wall charges on the envelope. It has been found that with the instant start circuit, a grounded metal fitting in close proximity to the lamp may render it unnecessary to provide a starting strip, although other treatment such as a water repellant coating, may be necessary.

An object of our invention is to provide an apparatus which will give reliable instant start without the aid of a grounded starting strip, water repellant coating, or grounded metal fitting.

In accordance with our invention, we include a choke which is tapped so as to divide it into two sections one sectionbeing in series with the supply conductor leading to one of the electrodes of the lamp and the other section connected to the other supply conductor and the other lamp electrode through a capacitor which may also serve as a power factor corrector.

Our invention will be better understood from the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

In the drawing, Fig. 1 illustrates diagrammatically a preferred form of the invention and Figs. 2, 3, and 4 show modified ways of connecting the tapped choke and capacitor to the thermionic electrodes of the lamp.

Referring to Fig. 1, there is shown a low pressure discharge lamp such as a fluorescent lamp 1, with fila-' mentary electrodes 2 and 3. These are heated by currents generated in secondary windings 4 and 5 of a transformer, the primary winding 6 of which may be connected in parallel with the lamp.

a A winding comprise'dfofaniron core choke 7. is ,tapped at a point along its length solthatiitrisldividedinto sections'9 and 10, and'a. capacitor 1 1.1is. connected between the end ofthe winding section 9 andl'the, remote 'sideof the mains. YThejinductances of sections19 and .10.:316

such that they do not resonate with the -c apacitor 11.- at

or near the supply. sfrequencyzvand .theinurnber .of .turns on section 10'is LgreaterQthan lthe numberof; turnson section 9.

Z'Figs'." 2,' 3flshow' variations in .the' connectionsrof the transformerwindings :heating the? lamp cathodes-to obtain decreasedand increased. lampstarting voltage respectively. 'QInFigs. 1,22, .and 3;.Ithe cathode. heating .current is reduced. whenLthelamp.strikes. owing toLthe reduction of the .transformersprimary,voltagel'sfromuapproximately mains volt-agetoayalue apprbxirnatelyeuual .-td .lamp voltage. drop. :In Big. .4,.. .however, is .shown a circuit ,in-which1the catho.de :heati g is not materially .re-

V .iduced whenl'the'ilampLstrikes aslthe primary winding" 6 is directlyacrossthe supply mains.

i On Qclosing switch; 8, t which is. .cserially =connected. be-

tweenfa.-snpplyf lead andlthenintermediate terminal. of l the choke... a. surgejof..current passing through the .wind- L ing" 9 commences,tojcharge,thecapacitor. 11..and,a.high

voltage pulse is induced in. WindingQlR-IflThe ,phase .relationship between windings'9 and10 is'such that the voltage across the winding 10 is additive to that in winding 9. At the instant of switching on, the voltage across the capacitor 11 is zero and the voltage surge induced in choke 7 appears between the lamp electrodes 2 and 3 breaking down the gas or vapor in the lamp and destroying inhibiting wall charges. The ionization remaining in the lamp enables an arc to be easily propagated down the tube and when the filamentary electrodes 2 and 3 heat up the lamp strikes.

A capacitor 12 may be connected across the lamp to suppress radio interference.

The capacitance of capacitor 11 may be of such value as to correct the power factor of the circuit to a value approaching unity.

While we have particular embodiments of our invention, it will be understood, of course, that we do not wish to be limited-thereto since many modifications may be made and we, therefore, contemplate by the appended claims to cover any such modifications as wall within the true spirit and scope of my invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. Apparatus for starting and operating an electric discharge lamp of the type having a pair of filamentary electrodes comprising, a filament supply transformer having a primary winding and two secondary windings, output leads respectively connected to said secondary windings, supply leads connected to said primary winding, a choke having three terminals one of which is in intermediate tap electrically nearer one end terminal than the other end terminal thereby dividing said choke into unequal turn sections, a capacitor connected between one of said supply leads and the end terminal of the smaller of said choke sections, said one supply lead also being connected to one of said secondary windings, the end terminal of the larger of said choke sections being connected to the other of said secondary windings, the other of said supply leads being connected to said intermediate tap terminal.

2. Apparatus for starting and operating an electric dis charge lamp of the type having a pair of filamentary electrodes comprising, a filament supply transformer having a primary winding and a pair of secondary windings connected respectively to each end of the primary winding, a choke having end terminals and an intermediate tap terminal for dividing it into unequal turn sections, a capacitor having one terminal connected to the end terminal of the smaller of said choke sections, leads connecting the end terminal of the larger of said choke sections and the other of said capacitor terminals respectively across said primary winding, and a pair of alternating current supply leads, one of said supply leads being connected to said other terminal of said capacitor, the other of said supply leads being connected to said intermediate tap terminal.

3. Apparatus for starting and operating an electric discharge lamp of the type having a pair of filamentary electrodes comprising, a filament supply transformer having a primary winding and two filament supply secondary windings one of which is directly connected to one end of said primary winding, and the other of which is insulated therefrom, .a choke having end terminals and an intermediate tap terminal for dividing the choke into unequal turn sections, a capacitor having one terminal connected to the end terminal of the smaller of said choke sections, the end terminal of the larger of said choke sections being connected to said insulated secondary winding, a pair of alternating current supply leads one of said supply leads being connected to said intermediate tap terminal, the other of said supply leads being connected to the other terminal of said capacitor and said one end of said primary winding, and a lead directly interconnecting said intermediate tap terminal and the other end of said primary winding.

4. In combination, an electric discharge lamp having a pair of filamentary electrodes, a choke having three terminals one of which is an intermediate tap electrically nearer one end terminal than the other end terminal thereby dividing said choke into unequal turn sections, at capacitor having two terminals one of which is connected to the end terminal of'the smaller of said choke sections, a pair of alternating current supply leads respectively connected to said tap terminal and the other of said capacitor terminals, leads connecting the end terminal of larger of said choke sections and said other capacitor terminal to said lamp electrodes respectively, a filament transformer having a primary winding and a pair of secondary windings, leads respectively connecting said secondary windings to said lamp electrodes, said primary winding being connected across one of the terminals of said larger choke section and said. other capacitor terminal.

References Cited in the file of this patent UNITED STATES PATENTS 1,975,770 Culver Oct. 9, 1934 2,056,647 De Bruin Oct. 6, 1936 2,231,584 Lord Feb. 11, 1941 2,256,242 Edwards Sept. 16, 1941 2,504,549 Lemmers Apr. 18, 1941 2,554,648 Stickley May 29, 1951 

